Process for subdividing solid particles



Patented Sept. 18, 1951 PROCESS FOR SUBDIVIDING SOLID PARTICLES KennethK. Kearby, Cranl'ord, N. J., assignor to Standard Oil DevelopmentCompany, a corporation of Delaware Application September 1a, 1946,Serial No. 697,810

3 Claims.

The present invention is concerned with'an improved process forsubdividing solid particles. The invention more particularly relates toan improved process for finely dividing or pulverizing carbonaceoussolid particles, as for example coal, which pulverized particles aresubsequently handled to produce gaseous products, as for example gaseousfuels, feed gases suitable for hydrocarbon synthesis reactions, and thelike. In accordance with my invention, I employ a standpipe arrangementwhich is of sufficient height to secure the desired fluid head necessaryto inject the particles to be finely divided into a high pressure fluidstream. The fluid stream containing the solid particles to be pulverizedis then passed through a jet pulverizing means.

It is known in the art to pulverize or finely divide solid materials,for example, carbonaceous materials, such as coal and the like, bypassing a stream of the material through a jet arrangement in which thepressure is reduced resulting in the pulverization of the material. Howver one disadvantage of these processes is that no satisfactorycontinuous method of introducing the solid particles into the fluidstream such as steam or air, has been obtained. Various suggestions havebeen made and attempts directed toward overcoming this problem andsecuring a satisfactory method of continuously introducing thecarbonaceous particles into the fluid stream. These efforts have nothowever been very successful.

I have now discovered a method of incorporating solid material into thefluid stream which is entirely satisfactory and which may be operated in.a continuous manner. In accordance with my invention I employ afluidized zone of sufllcient height to secure thedesired fluid head.From the bottom of my standpipe arrangement, I introduce suspended fluidsolid particles into the fluid stream as for example steam, and thenpass this high pressure stream through a jet arrangement in which thepressure is substantially reduced resulting in the pulverization of thesolid material.

The process of my invention may be readily understood by reference tothe attached drawing illustrating a modification of the same. For thepurpose of illustration the operation described with respect to thedrawing is assumed to be a coal pulverization process. Referringspecifically to the drawing carbonaceous solid material, as for examplecoal, is introduced into hopper arrangement III by means of conveyorline or equivalent means I. The feed coal falls downwardly in zone Itand contacts upflowlng suspending gases which are introduced into zoneID by means of line 2 and distributed throughout the zone bydistributing means 3. The velocity of the upflowing gases is sufllcientto maintain the solid particles in a fluid ebullient state, the upperlevel of which is at point A. The velocity of upfiowing gases isgenerally in the range from about 0.5 to 2.0 ft./sec. Although the sizeof the solid particles introduced into zone l0 may vary considerably,for the purpose of illustration, it is assumed that these particles havea, particle size in the range from about 20 to mesh. Additionalsuspending gases may be introduced if necessary at points i. Thesuspending gases pass upwardly through zone l0 and are withdrawn bymeans of line 5 after passing through a cyclone or equivalent separatingmeans '6. Entrained solid. particles separated in cyclone separator tare returned to the bed by means of line I. Larger particles which arenot suspended fall past distributing means 3 and are removed from zoneI0 by means of line '8. These particles may be passed through mechanicalcrushing means 9 and recycled to the top of zone it by means of line H.These larger particles may also be withdrawn from the system by means ofline l2.

In accordance with my process, I withdraw fluidized particles from zoneIt through standpipe arrangement it which is shown as a broken conduitto indicate that its length may vary appreciably. The suspended coalparticles having a fluid head proportional to the size of th particles,the density of the particles per cubic foot, and the length of thestandpipe itself are introduced into line It through which gaseousfluids are passed. For the purpose of illustration, the gaseous fluidpassed through line I comprises steam. The steam containing thefluidized coal particles is passed through jet arrangement l5 positionedin pulverizing zone 20. As the gases pass through jet arrangement 15 thepressure on the gases and on the coal is substantially reduced resultingin the pulverization of the coal. The suspending gases and thepulverized coal pass upwardly through cyclone separator or equivalentmeans l6 positioned in the upper section of zone 20. The steam and thefinely divided coal particles are withdrawn from zone 20 by means ofline H and may be handled in any manner desirable. Larger particlesremoved from the suspending gases in cyclone separator [6 are withdrawnby means of line It and preferably recycled to the top of zone In by anysuitable conveying means. Larger particles which are not pulverized asthey pass through jet arrangement I! are collected in the bottom 01'zone 20 and removed by means of line I 9. These particles are likewiserecycled to the top of zone Hi.

My process may be applied to any operation wherein it is desired toflnely divide solid pargreater than the pressure within the line into awhich the fluidized solids are being fed. This, as pointed outpreviously, will depend upon the particular solids being fluidized, thepounds per cubic foot, and the height of the standpipe itself. In aprocess designed for the pulverizatioh of coal it is preferred that thepressure in the steam line be in the range from about 60 to 100 poundsper sq. inch, and that pressures in the expansion zone after the jet beabout atmospheric pressure. Under these conditions the height of thestandpipe will be in the range from about l'to 200 it.

If the particles introduced into zone are relatively large it may benecessary to introduce flner particles in order to secure adequateparticle size distribution. These finer particles may be secured from anexternal source and introduced by means of line '21, but are preferably7 secured by segregating a portion of the particles withdrawn from zone20 and introducing these pulverized particles into zone I0 by means ofline 22.

It is to be understood that the apparatus may be modified. For example,line l3 may be lowered within zone 10 so that coarse material would beallowed to fall downwardly through the bed in zone l0, be withdrawn fromthe bottom of zone III by means of line l3 and passed through jetarrangement as described. It is also within the concept of my inventionto employ a downwardly moving bed in zone In of larger nonfluidizedparticles with fluidized solid particles interspersing between theinterstices of the larger particles. In other words, the bed within zonel0 would comprise nonfiuidized solid particles and fluidized solidparticles in which all particles were moving downwardly. The onlyrequirement is that no particles would be too large so that it could notpass through the jet. It is also within the scope of m invention to passthe solids to be pulverized directly to jet means 15.

The process or my invention is not to .be limited by any theory as tomode of operation, but only in and by the iollowing claims in which itis desired to claim all novelty insofar as the prior art permits.

Y I claim:

1. Process for dividing solid particles whic h comprises introducingsaid particles into a hopper zone, maintaining said particles in saidhopper zone in a fluidized state, whereby the larger of said particlessegregate at the bottom or said hopper zone, withdrawing said largerparticles from the bottom of said hopper zone, mechanically breaking thesame and returning the same to an upp r point or said hopper zone,withdrawing fluidized particles from an intermediate point in saidhopper zone, introducing said particles into a fluid stream, maintainingsaid fluid stream under pressure, passing said fluid stream and saidintroduced solid particles through a jet positioned in a pulverizingzone under conditions to substantially reduce the pressure on said fluidstream whereby said solid particles are subdivided.

2. Process as defined by claim 1 wherein said particles are carbonaceousparticles.

3. Process as defined by claim 1 wherein said particles comprise coalparticles, and wherein said fluid stream comprises steam.

rcamwrn x. KEARBY.

REFERENCES CITED The following references are 01. record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,539,401 Neuburger May 26, 19251,616,547 Pontoppidan Feb. 8, 1927 1,875,531 Walton Sept. 6, 19321,922,313 Mason Aug. 15, 1933 2,032,827 Andrews Mar. 3, 1936 2,237,091Stephanofl Apr. 1, 1941 2,272,564 Kuever Feb. 10, 1942 2,311,564 MundayFeb. 16, 1943 2,327,175 Conn Aug. 17, 1943 2,341,193 Scheineman Feb. 8,1944 2,379,027 Monro June 26, 1945 2,392,866 Stephanofi Jan. 15, 1946FOREIGN PATENTS Number Country Date 216,476 Switzerland Dec. 1, 1941546,088 Great Britain June 26, 1942 591,921 Great Britain Sept. 2, 1947

